Effect of enhanced macrophage function on early wound healing

Although the macrophage is important to wound healing, research has focused on its relationship to fibroblast and collagen synthesis. This study was designed to assess effects of enhanced macrophage function on early wound healing, before established collagen synthesis. Sprague-Dawley rats had dorsal incisions after one of three treatment regimens: (1) saline solution, 0.5 ml administered intravenously, (2) intravenous glucan, a macrophage stimulant, 20 mg; (3) topical glucan, 20 mg. Intravenous therapy was administered 24 hours before and after incision. Breaking strength was significantly increased (p less than 0.01) by both intravenous glucan (49.8 +/- 5.5 gm) and topical glucan (59.7 +/- 5.6 gm) on the fourth day after incision, compared with controls (22.0 +/- 2.6 gm). Similar results occurred on the seventh day after incision. Although formalin fixation significantly enhanced breaking strength in fresh control wounds (22.0 +/- 2.6 vs 39.5 +/- 2.2 gm), no increase occurred in wounds treated with intravenous glucan (49.8 +/- 5.0 vs 55.3 +/- 6.4 gm), indicating maximal cross-linking of collagen. Collagen synthesis, reflected by tritiated proline uptake, was no different in control versus glucan groups. Supernatants from control or glucan-activated macrophages were injected intraperitoneally or applied topically in the rat model. Activated supernatant, both intraperitoneal and topical, resulted in increased breaking strength on the fourth day after incision. Formalin fixation did not increase breaking strength in the activated supernatant groups. We conclude that enhanced macrophage function increases early wound breaking strength. This effect appears unrelated to collagen synthesis but may be related to increased cross-linking of collagen. Similar effects are seen with activated macrophage secretory products administered intraperitoneally or topically.